Dental restorative materials have the potential both for local toxicity and undesirable systemic side effects through the release of components, reaction intermediates, or degradative products into the biophase. Resin composites are a class of dental restoratives which are now very widely used. There is no evidence that any adverse systematic effects are associated with the resins. However, local effects on dental pulp, including pulpal pain and death, have been widely reported. We seek to clarify whether chemical release from the materials may contribute to these local effects. The specific aims in the project period are to quantify the release of resin composite components from a range of materials, and to seek correlation between the amounts released and the toxic effects of individual components and of aqueous eluates of whole resin samples. High performance liquid chromatography will be used to quantify the release. Variations in the pattern of release of these and other components both directly into aqueous solution and through dentin will then be determined for a number of clinically relevant variables. Concentrations of components within dentin immediately adjacent to the odontoblast layer will also be determined in teeth restored with resin composite, both in vitro and in vivo. The longterm goal is to improve safety and effectiveness of dental restorative materials. The proposed work will provide data directly relevant to the future formulation and to the clinical use of dental resin composites. It will also add to concepts and methods which will be applied to the study of other restorative materials as they are developed.